How much time do we have on Earth?

If we want to explore the possibility of humans colonizing another planet, one of the first questions to ask is how much time we might have to figure out how to do it.  So how much time might we humans have on this planet which at present is our only home?

The most optimistic answer is about two billion years.  At that point, the sun will begin to burn out, and in its death throes will first become much larger.  At that point, Earth will get so hot that we would be incinerated.  Two billion years, though, is a pretty good chunk of time, about as long as multi-cellular life has already colonized Earth.

But we may have a good deal less time than that.  Species last on average about two million years, though simpler organisms tend to last longer, and more complex organisms, like us, often last for shorter periods than that.  How old we humans as a species are is not exactly clear, but the oldest estimate is that homo sapiens cannot be more than a quarter of a million years old.  If homo sapiens survives as long as an average species, though, we should still have 1.75 million years ahead of us.  Not two billion, but nonetheless, still time to achieve a lot.

Earth, however, may not remain habitable for creatures like us humans for that long.  The climate is always changing, moving from extremes of cold to weather that is warm enough to melt away all the ice everywhere.  The atmosphere also changes, including, critically, levels of oxygen.  The availability of water is not constant, so deserts and forests come and go.  Earth even passes through strong fields of radiation about every 250 million years, which could make life difficult for us.

How much of our current climate change is due to human activity, and how much is do to the activity of the Sun, geothermal exchanges, volcanoes, ocean currents and extra-terrestrial bodies is not clear.  However, scientists estimate that if climate change continues at its present rate of change (whatever the reason), and we do not radically alter our life styles on a global scale, we will seriously begin to feel constraints on the way we live by 2050.  At some point we will start fighting for our very lives over water and food. 

Barring a major meteor strike or a series of events leading to vast eruptions of nitrogen from the ocean depths that would destroy our oxygen supply, global warming in itself, while possibly causing millions to die, are not expected to lead to the extinction of all human life.  It is not inconceivable that the current trends could lead to more drastic changes, which could make all human life impossible, but changes on that scale are not imminent.  But even initial changes that occur within the next 40 or 50 years could slow down our economies drastically, which means we will have fewer resources to spend on exotica like space exploration – without which we will never be able to colonize another planet, even assuming we can find one to colonize.

So instead of billions, or millions, or even thousands of years, we may something closer to a century to manage a move to another planet.  The paradox is that the better care we take of the planet we already have, the more time we are apt to have to find another one.

Can we do it in time?  how much time do we need?  how much time do we have?


About Terry Sissons

Terry Sissons is the author of The Big Bang to Now: All of Time in Six Chunks, and this blog is a dialogue about the universe and what’s happened in the last 13 billions years.
This entry was posted in beyond earth, saving our home - thoughts about global warming. Bookmark the permalink.

5 Responses to How much time do we have on Earth?

  1. Ceci says:

    Terry Sissons, you have it all wrong.

    God is the Creator and Maker of all things and it was he who established the human race, not 13 billion years of evolution. Besides, evidence in stars, rocks, and the oceans all support Creation by God. Maybe you need figure out what the truth is before writing a book and terrorizing the human population into thinking the world is going to end.

  2. Junior says:

    Ceci, I disagree with every word you wrote.
    Things are not, and will never be as simple as “God made it that way”.

    Thinking like this only will lead us to waste our precious time.

    You and your god had your time. It was during the dark ages. What have you accomplished then? I tell you: Inquisition.

    • Ceci may very well have a different response to your comment than mine. But I agree that “God made it” does not necessarily say everything there is to be understood about anything. In fact, it is possible to be deeply religious and believe that the exploration of the world – including how the universe began – was an act of praise of the God who made it. The earliest scientists certainly felt that they were praising God with their scientific explorations. Many scientists today still do.
      Terry Sissons

  3. Adewole opeyemi says:

    terry sissons,i honestly disagree with you.According to genesis(a book in the bible)God created everything.scientist dont believe in spiritual things.the world will never end,only sinners will perish.but the good ones will inherit the earth forever.So i agree with ceci.The probabily 4 God existence is one. adewole opeyemi. 6

    • I have very familiar with Genesis, as I am with all the bible, for which I have a great respect. Our difference of opinion is in how the bible should be interpreted. I believe that God spoke to the Hebrew people in their own language, and that language often made use of metaphor and symbols to communicate the truth. An example of this is the parables which was one of Jesus’ most powerful forms of communicating, but which were never meant to be understood literally. Understanding any parable literally would miss the entire point, wouldn’t it?

      Historically, this is how Christians also interpreted the bible until just a few centuries ago. The early church fathers did not interpret the bible, including Genesis, literally.

      You say that scientists don’t believe in spiritual things. That is not quite true. When science was developing in Europe in the 15th century, the political power of the Roman Catholic Church was almost unchallenged. What scientists of the day said was that their study of science did not infringe on the spiritual authority of the church. They did not say that they did not believe in spiritual things — most of them did. (In fact, many of the great scientists were themselves ordained ministers with congregations and a strong spiritual life. Many scientists today also believe in spiritual things and practice their religion. What scientists do say is that the scientific method is not a method that can be applied to the spiritual world. We must use symbols and poetry, our intuition, and if you prefer, faith, to understand the world which many call spiritual.

      I think, therefore, it is quite possible to mine the greatest truths of the bible without believing that God ever meant it to be understood literally. God was revealing something much more profound than that.

      What do you think?

      Terry Sissons

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